The invention relates to amplifiers and buffers, particularly for driving a signal onto a power line.
The present invention is an improvement of an amplifier disclosed in U.S. Pat. No. 5,241,283 which is discussed in conjunction with FIGS. 1 and 2 of this application.
An improvement in a input/output buffer for transmitting a communication signal over a power line is described. The buffer includes a transmit filter which receives an input from a digital-to-analog converter. The output stage of the buffer has a first pair of emitter followers for driving an output in a first direction and a second pair of emitter followers for driving the output in the opposite direction. The improvement of the present invention comprises maintaining the collector-to-emitter voltage constant without degrading the ability to provide an output signal nearly equal to the supply potential. This substantially reduces the distortion associated the prior art amplifier.